See "Dithering" with Ubuntu 22.04 / MD Radeon Pro WX 3200 / ViewPIXX - #9 by jamespherman
→ Fixed by myself and fix in all distros since 11th October 2022.
→ Affected Polaris gpu family, e.g., WX4100, WX5100 for a couple of months.
Long solved on Linux, ofc. at a financial loss of over 1000 Euros to the PTB project at that time.